At present, there are two paging modes in CDMA system, which are slotted mode and non-slotted mode. The non-slotted mode refers to an operating mode under which a mobile station monitors a forward-paging channel (F-PCH) continuously rather than monitors the F-PCH according to a specific slot.
As the mobile station needs to continuously demodulate and decode the F-PCH, and deal with the messages in the F-PCH, the electricity in batteries is quickly consumed; further, when there is no paging on the F-PCH, the system will circularly broadcast system parameter messages. For a mobile station that has correctly obtained these parameters and is in an idle state, it is also a waste to receive these parameters repeatedly.
Therefore, in order to reduce unnecessary monitoring of a mobile station on the F-PCH and lengthen the service time of the batteries in an idle state, IS-95 specifies a slotted mode. The slotted mode may correspond to the non-slotted mode. When operating in the slotted mode, a mobile station in an idle state does not continuously monitor the F-PCH. Instead, it monitors the F-PCH within a specific time period every specific time interval according to specific rules, and at the interval between monitoring of the F-PCH, the mobile station is equivalently in a sleep state, that is, baseband processor and radio-frequency (RF) circuit reduce or even stop working, thus power consumption can be lowered.
In the slotted mode, the basic unit for time division is slot of the F-PCH. The duration of a slot is 80 ms, that is four 20 ms PCH frames. Under the slotted mode, a mobile station in an idle state usually monitors F-PCH once every specific time interval, and this time interval is called slot cycle, in which usually one or two slots are monitored. The length of a slot cycle is calculated with 1.28 s (=16×80 ms) as a unit, and it must be 1, 2, 4, 8, 16, 32, 64 or 128 times of 1.28 s. If the length of a slot cycle is expressed with T, then T=1.28×2i s, wherein i is slot cycle index and the value of which may be an integer from 0 to 7, while the maximum value of a slot cycle may be 2048 slots, i.e., 163.84 s. Moreover, a subscriber may adjust the length of a slot cycle through setting the slot cycle index of the mobile station by himself. After adjustment, the length of a slot cycle will be reported to the system through parameter change registration, calling, paging response or other messages.
Further, for the subscriber, the adjusting range of the slot cycle s restricted by the current network configuration. In the system parameter messages of a mobile station in a broadcasting service area, there is a parameter which is the max slot cycle index. This index specifies the maximum slot cycle allowed to be used in the current system, and the slot cycle index actually used by the mobile station needs to be determined according to the actual condition.
As described above, under the slotted mode, a mobile station monitors paging only in a specific time and generally only monitors one or two time slots in a PCH slot cycle, thus power consumption of the mobile station is reduced, and the lifetime of the battery is lengthened. On the other hand, under the non-slotted mode, a mobile station needs to monitor all paging slots.
In a trunking system, in addition to slot cycle index and other parameters of the original system, max PTT (Push To Talk) slot cycle index is also introduced, which specifies the maximum slot cycle index and other parameters allowed to be used in the current PTT system.
Further, in PTT system, various reasons can contribute to a problem of slow access when a mobile station is called after power-on, which restricts PTT call and other functions. However, no technical scheme that can solve this problem is available at present.